The present invention is directed to compounds and compositions containing said compounds which bind selectively to somatostatin receptor subtypes and the use of said compounds for treating medical disorders which are mediated by somatostatin receptor subtypes. Somatostatin (somatotropin release inhibiting factor, SRIF), a tetradecapeptide hormone, originally isolated from bovine hypothalami (Brazeau, P. et al. Science 179, 77-79, 1973) has been shown to have a wide range of regulatory effects on the release of a variety of hormones such as growth hormone, prolactin, glucagon, insulin, gastrin (Bloom, S. R. and Poldack, J. M., Brit. Med. J. 295, 288-289, 1987). In addition, antiproliferative properties (Reichlin, S., N. Eng. J. Med. 309, 1495-1501, 1983) have been obtained with somatostatin analogs in metastatic prostatic cancer (Parmar, H. et al, Clin. Exp. Metastasis, 10, 3-11, 1992) and in several other neuroendocrine neoplasms in man (Anthony, L et al. Acta Oncol., 32, 217-223, 1993). Metabolism of somatostatin by aminopeptidases and carboxypeptidases leads to a short duration of action.
The actions of somatostatin are mediated via membrane bound receptors. The heterogeneity of its biological functions has led to studies to identify structure-activity relationships of peptides analogs at the somatostatin receptors which resulted in the discovery of five receptor subtypes (Yamada, et al, Proc. Natl. Acad. Sci. U.S.A., 89, 251-255, 1992; Raynor, K et al. Mol. Pharmacol., 44, 385-392, 1993). The functional roles of these receptors are under extensive investigation. Binding to the different types of somatostatin subtypes have been associated with the treatment of the following conditions and/or diseases. Activation of types 2 and 5 have been associated with growth hormone suppression and more particularly GH secreting adenomas (Acromegaly) and TSH secreting adenomas. Activation of type 2 but not type 5 has been associated with treating prolactin secreting adenomas. Other indications associated with activation of the somatostatin subtypes are restenosis, inhibition of insulin and/or glucagon and more particularly diabetes mellitus, hyperlipidemia, insulin insensitivity, Syndrome X, angiopathy, proliferative retinopathy, dawn phenomenon and Nephropathy; inhibition of gastric acid secretion and more particularly peptic ulcers, enterocutaneous and pancreaticocutaneous fistula, irritable bowel syndrome, Dumping syndrome, watery diarrhea syndrome, AIDS related diarrhea, chemotherapy-induced diarrhea, acute or chronic pancreatitis and gastrointestinal hormone secreting tumors; treatment of cancer such as hepatoma; inhibition of angiogenesis, treatment of inflammatory disorders such as arthritis; chronic allograft rejection; angioplasty; preventing graft vessel and gastrointestinal bleeding. Somatostatin agonists can also be used for decreasing body weight in a patient.
In drug research, it is a key issue to minimize side effects by developing highly potent and selective drug molecules. Recent work on the development of nonpeptide structures (Hirschmann, R. et al, J. Am. Chem. Soc. 115, 12550-12568, 1993; Papageorgiou, C. and Borer, X., Bioorg. Med. Chem. Lett. 6, 267-272, 1996) have described compounds with low somatostatin receptor affinity.
The present invention is directed to a family of nonpeptide compounds, which are selective and potent somatostatin receptor ligands.